It is known in the art that devices operating at high speeds, devices operating at high clock frequencies, and/or devices which require extremely long conductive interconnections suffer from a performance-reducing phenomenon referred to as a known and understood signal reflection or transmission line effect problem. If a zero volt signal is changed to a five volt signal, for example, on a conductor or bus which is either long in length or operating at a fast edge rate, if the bus or conductive line is not properly terminated via an impedance, the conductive line or bus will take time to settle to the 5 volt value from the 0 volt value due to one or more reflections off one or both ends of the bus. To reduce signal reflection and thereby improve performance, permanent resistors have been placed at the ends of uni-directional buses to reduce signal reflection. This uni-directional termination is easy to do since only one end of the bus is ever receiving data (the other end is always sending) and therefore termination of the receiving side is all that is required. Unfortunately, if the bus is idle or the part is in a low power mode of operation, the connected permanent resistor usually caused increased power consumption which is disadvantageous.
In a bi-directional bus, the termination problem is enhanced because either end of the bus may either be receiving or transmitting at any time. Therefore, in the prior art, permanent resistor termination is placed at both ends of the bus and are connected regardless of whether or not they are needed. This results in an increased load to the bus and increased power consumption when the bus is placed into a low power mode of operation.